1. Field of the Technology
The present disclosure relates to equipment and techniques for forging die heating. The present disclosure more specifically relates to equipment and techniques for heating a forging surface of a forging die.
2. Description of the Background of the Technology
A work piece, such as an ingot or a billet, for example, can be forged into a particular configuration or shape using a forging die. Forging dies can comprise open-faced forging dies, closed-faced or “impression” forging dies, or other suitable forging dies. Most open-faced forging dies can comprise a first or a top portion and a second or a bottom portion. In general, the bottom portion can act as an “anvil” or a stationary portion, while the top portion can act as the “hammer” or a movable portion as it moves toward and away from the bottom portion. In other open-faced forging dies, both the top and the bottom portions can move toward each other or, in still other configurations, the bottom portion can move toward a stationary top portion, for example. The movement of the top or bottom portions of the forging die can be accomplished through the use of pneumatic actuators or hydraulic actuators, for example. In any event, the top and bottom portions of the forging die can be disposed in an open position, where they are spaced a suitable distance from each other, and in a closed position, where they contact or nearly contact each other.
During the forging process, a portion of the work piece can be positioned between the top portion and the bottom portion of the forging die and forged by force applied by the top portion and/or the bottom portion. Applying such force to the work piece can change the structural properties and/or the crystalline structure of the work piece, such as through work hardening, thereby possibly developing weak spots in the work piece. Work hardening, for example, may be inhibited if the work piece is heated to a suitable temperature prior to or during the forging process. Heating of the work piece can make the work piece more malleable such that it can be forged using less force applied by the top and/or the bottom portions of the forging die. Depending on the composition of the work piece, the work piece can be heated to a temperature in the range of 1800-2100 degrees Fahrenheit, for example, prior to being forged, to facilitate forging of the work piece. As can be seen, various benefits may be achieved by heating the work piece prior to and/or during forging.
In addition to the heating of the work piece prior to and/or during forging, in some instances, the top and/or bottom portions of the forging die can also be heated to reduce or minimize any temperature differential between the heated work piece and the top and bottom portions of the forging die. Through such heating, surface cracking of the work piece during forging can be reduced relative to forging using a forging die at ambient temperature (20-25 degrees Celsius). For example, if a region of a work piece heated to a temperature of 1800-2100 degrees Fahrenheit contacts a forging die at ambient temperature, the significant temperature differential reduces the temperature of the work piece region and adjacent regions. The significant temperature differential can create mechanically weak regions within the work piece that may make the work piece unsuitable for its intended application. Further, in some instances, the significant temperature differential between forging die and work piece can lead to inclusions in the work piece caused by non-uniform cooling of the work piece during and after forging if the region of the work piece contacted by the ambient temperature forging die cools faster than the rest of the heated work piece.
In an attempt to minimize these negative consequences, referring to FIG. 1, certain forging techniques employ a single torch 2 aimed at a forging die 4 to preheat much or all of the forging die 4 prior to forging a work piece (not illustrated). This single torch 2 can be a natural gas or a propane air-aspirated torch, for example. Because a single torch 2 is used, this forging die preheating technique can take several hours or longer and may only heat the forging die 4 to a temperature in the range of 600-800 degrees Fahrenheit, for example. In most instances, the forging die 4 is heated with the top portion 6 and the bottom portion 8 of the forging die 4 in a closed, or substantially closed, position. As such, the single torch 2 can be moved vertically about a side surface 9 of the top and bottom portions 6 and 8 of the forging die 4 in the directions indicated by arrow “A” and arrow “B”, for example, to heat the forging die 4. Also, the single torch 2 can be moved horizontally about the side surface 9 of the top and bottom portions 6 and 8 of the forging die 4 in the directions indicated by arrow “C” and arrow “D”, to heat the forging die 4. In other embodiments, the single torch 2 can be moved both horizontally and vertically about the side surface 9. Of course, the single torch 2 can also be moved about the side surface 9 of the forging die 4 in any other suitable direction or can remain stationary.
Such preheating of the forging die, although helpful in the forging process, can lead to non-uniform heating of the forging die 4 or a forging surface 5 of the forging die 4, again possibly resulting in inclusions or weak spots in the work piece where the forging die 4 contacts and cools the work piece. Another issue with the above-described preheating practice is that, even though the forging die 4 can be heated to about 600-800 degrees Fahrenheit, there can still be a substantial temperature differential between the work piece, which may be at forging temperatures of about 1800-2100 degrees Fahrenheit, and the forging die 4. The existence of a significant temperature differential between the work piece and the forging surface 5 can sometimes lead to surface cracking of crack-sensitive alloy work pieces, such as Alloy 720, Rene '88, and Waspaloy, for example. Further, the non-uniform cooling produced by temperature differentials can, in some instances, cause inclusions or weak spots within work pieces of these alloys.
Given the drawbacks associated with conventional forging die pre-heating techniques, it would be advantageous to develop alternative pre-heating techniques.